The invention relates generally to resistors and more specifically to an arrangement for compensating for temperature dependent variations and process variations in surface resistance of resistors on a chip.
When filters are produced on silicon chips, there are a number of factors that influence the transfer function of the filters. Since it is the RC-constant that sets the cut-off frequency of a filter, one can look at what causes the R, i.e. the resistance, and the C, i.e. the capacitance, to change.
The surface resistance of a resistor varies with temperature. Moreover, the surface resistance can vary in response to variations in the production process. The width of the resistor on the chip can e.g. vary.
In total, the resistance value can vary more than xc2x150%.
The capacitance value varies merely marginally and does not need compensation in the same extent.
The object of the invention is to provide an arrangement for compensating for such temperature dependent variations and process variations in surface resistance of a resistor on a chip.
This is attained in accordance with the invention by automatically connecting one or more compensating resistors in series with a main resistor.